There are no extensions showing within Safari preferences but I have Kaspersky Internet Security installed and I think that adds "extensions" to Safari.

The issue remains if Kaspersky is running or not

The only thing I can link it to is I've started a small business and I've been using a domain providers control panel to edit my website, and also started to use a service called Setmore which I've added bookmarks for. I might try removing these to see if it makes a difference.

--- Post Merged, Jan 24, 2017 ---

Just followed some steps I found on another topic which seems to have solved the issue...

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